Metallurgy



Patented Jan. 16, 1945 METALLURGY Marvin J. Udy, Niagara Falls, N. Y.

N Drawing.

Application July 9, 1942,

Serial No. 450,283

21 Claims.

This invention relates to metallurgy and has for an object the provision of improved metallurgical methods or processes and improved metallurgical products. More particularly, the invention contemplates the provision of certain improvements in methods or processes for incorporting alloying elements in molten metals such as iron and steel and the provision of improved exothermic reaction mixtures for use in incorporating alloying elements in molten metals. The invention further contemplates the provision oi certain improvements in methods for producing exothermic reaction mixtures for use in incorporating alloying elements in molten metals.

The expressions alloying element" and alloying elements are employed herein to describe an element and elements of the group of metallic elements consisting of chromium, manganese, vanadium, tungstemmolybdenum, titanium and zirconium, which elements are employed commonly as alloying additions to iron and steel. The

aforementioned alloying elements usually are marketed in the form of ierro-alloys, that is, metallic alloys comprising the alloying elements and iron or comprising the alloying elements, iron and silicon.

According to some heretofore customary practices, the alloying elements are incorporated in molten metals by adding the ferro-alloys in either the solid state or the molten state directlyto the molten metals. It has been proposed also to incorporate alloying elements in molten metals by adding to the molten metals exothermic reaction mixtures comprising the ferro-alloys. In the production and use of such exothermic reaction mixtures in accordance with heretofore customary practices, considerable difliculty has been encountered because of th fact that the metallic alloying elements are readily oxidizable and because of the necessity for employing strong oxidizers which tend to oxidize the alloying elements upon ignition with resulting low recoveries of the alloying elements.

According to the present invention, alloying elements are incorporated in molten metals by igniting in contact with the molten metals exothermic reaction mixtures comprising the alloying elements, iron, silicon and sodium nitrate and in which the silicon and sodium nitrate are present in controlled amounts and proportions. Exothermic reaction mixtures of the invention comprise, and may consist of, an alloying element, iron, silicon and sodium nitrate. The silicon and sodium nitrate are provided primarily for the purpose of generating by reaction sufilcient heat to melt the alloying element and the iron. An excess of silicon in addition to that required for reaction with the sodium nitrate may be provided, or, in other words, an'amount of sodium nitrate somewhat less than that required to oxidize all of the silicon may be provided. The alloying element may be-employed in the form of a ferro-alloy free of, or substantially free of, silicon or it may be employed in the form of a ferro-alloy containing all or a. substantial portion of the silicon required for the reaction mixture. Any silicon required in addition to that of the ferro-alloy may be provided in the form of ferrosilicon.

An exothermic reaction mixture of the invention, for example, may comprise, or may consist o1,

(1) Sodium nitrate and one or more of the following ferro-alloys:

Ferrochrome silicon (FeCrSi) Ferromanganese silicon (FeMnSi) Ferrovanadium silicon (FeVaSi) Ferrotungsten silicon (FeWSi) Ferromolybdenum silicon (FeMoSi) Ferrotitanium silicon (FeTiSi) Ferrozircomum silicon (FeZrSi), or

Sodium nitrate, ferrosilicon and one or more of the following ferro-alloys: Ferrochromium (FeCr) Ferromanganese (FeMn) Ferrovanadium (FeVa) Ferrotungsten (FeW) Ferromolybdenum (FeMo) Ferrotitanium (FeTi) Ferrozirconium (FeZr), or

Sodium nitrate, one or f erro-alloys Ferrochrome silicon (FeCrSi) Ferromanganese silicon (FeMnsi) Ferrovanadium silicon (FeVaSi) Ferrotungsten silicon (FeWSi) Ferromolybdenum silicon (FeMoSi) Ferrotitanium silicon (FeTiSi) Ferrozirconium silicon (FeZrSi) (4) more of the following and one or more of the following ferro-ailoys: Ferrochromi-um (FeCr) Ferromanganese (FeMn) Ferrovanadiu-m (FeVa) Ferrotungsten (FeW) Ferromolybdenum (FeMo) Ferrotitanium (FeTi) Ferrozironium (FeZr), or Sodium nitrate, ferrosilicon, one or more of the following ferro-alloys:

Ferrochrome silicon (FeCrSi) Ferromanganese silicon (FeMnSi) Ferrovanadium silicon (FeVaSi) Ferrotungsten silicon (FeWSi) Ferromolybdenum silicon (FeMoSi) Ferrotitaniurn silicon (FeTiSi) Ferrozirconium silicon (FeZrSi) and one or more of the following ferro-alloys:

Ferrochromi-um (FeCr) Ferromanganese (FeMn) Ferrovanadium (FeVa) Ferrotungsten (Few) Ferromolybdenum (FeMo) Ferrotitanium (FeTi) Ferrozirconium' (FeZr) The present invention is based upon my discovery that a higher recovery of alloying element or elements may be obtained upon ignition of an exothermic reaction mixture consisting essentially of one or more alloying elements, iron, sili. con and sodium nitrate when the sodium nitrate and the silicon are present in the reaction mixture in proportions by weight equivalent to not more than 2.42 parts of sodium nitrate to 1.0 Part of silicon. The results of my investigations indicate that sodium nitrate and silicon, when present in intimate admixture in an exothermic reaction mixture, probably react upon ignition of the reaction mixture in accordance with the following equation requiring sodium nitrate and silicon in proportions by weight equivalent to about 2.42 parts oi sodium nitrate to 1.0 part of silicon:

Exothermic reaction mixtures containing sodium nitrate and silicon in the aforementioned ratio and in amounts such as to be capable of developing or generating the desired quantity of heat are capable, under ideal conditions with respect to particle sizes, intimate mixing and reaction environment. of reacting upon ignition to oxidize substantially all of the silicon without substantial oxidation of metallic alloying elements which may be present in the mixtures.

For practical reasons, I prefer to express the aforementioned ratio as, about 2.5 parts by weight of sodium nitrate to 1.0 part by weight of silicon, and, in the preparation of exothermic reaction mixtures in accordance with th invention, I prefer to simplify the calculati ns and procedures by employing about 2.5 parts by weight of sodium nitrate for each part by weight of silicon which I propose to oxidize or burn upon ignition of the reaction mixtures. The improved recoveries capable of being accomplished by the invention are illustrated by the following results obtained by igniting in contact with similar quantities of similar steel three different exothermic reaction mixtures cons sting of ferrochrome silicon (Cr 52.0%; Si 6.55%; balance Fe) and sodium nitrate, each mixture containing sufllcient chromium to form alloy steel containing twelve percent (12%) of chromium and the same amount of silicon but containing d fferent quan- 'tities of sodium nitrate to provide sodium nitrate to silicon in theratios, 2.5 to 1.0; 3.0 to 1.0; and

Per cent Pgr cent Plelr cent silligon c romc rompc -up Nitrate to silicon ratio um in um per one not steal recovery cent of chromium Exothermic reaction mixtures of the invention are formed by providing sodium nitrate in amount not greater than about 2.5 parts by weight of sodium nitrate for each part by weight of silicon to be incorporated in the mixture and mixing the components intimately. The components preferably are in th form of particles all of which, or a large proportion of which, say about ninety percent more or less, are small enough to pass a loo-mesh screen. Mixing may be effected advantageously by grinding the components together in a ball mill or other suitable grinding apparatus. Silicon and sodium nitrate preferably are provided in amounts and proportions, relatively to other components, such that reaction of the sodium nitrate and silicon upon ignition of the reaction mixture will generate sufficient heat to melt the other components.

The actual proportions by weight of sodium nitrate to silicon employed will depend to some extent upon the results sought to be accomplished. Reaction mixtures consisting of lowsilicon ferrochrome silicon and sodium nitrate containing sodium nitrate and silicon in the ratio of about 2.5 to 1.0 will show upon ignition in contact with molten steel a silicon pick-up in the steel of about 0.03 percent of silicon for each percent of chromium incorporated in the steel. Such a silicon pick-up affords protection against oxidation of the chromium and is not objectionable to steel makers. Higher silicon pick-up can be obtained by employing lower ratios of sodium nitrate to silicon. The amount of silicon oxidized by sodium nitrate in the use of any reaction mixture preferably is not substantially greater than that required to provide the heat necessary for melting the other components under the conditions of use of the mixture. In general, oxidation of about five to ten parts by weight of silicon for one hundred parts by weight of other components to be melted will result in efiective melting.

Reaction mixtures of the invention may be employed in powder form or in the form of solid agglcmerates. When employed in the form of solid agglomerates, the agglomerates may be prothe molten metals in any suitable manner, as for example, by adding the mixtures to molten metals in ladles or furnaces or by placin the mixtures in ladles and thereafter pouring the molten metals into the ladies.

I claim:

1. An exothermic reaction mixture for use in incorporating an alloying element in molten metal consisting of iron, an alloying element, silicon and sodium nitrate, the sodium nitrate and the silicon being present in the reaction mixture in proportions by weight equivalent to not more than 2.5 parts of sodium nitrate to 1.0 part of silicon and in amounts such as to be capable upon ignition of the reaction mixture of generating by reaction sufficient heat to melt the iron and alloying element.

2. An exothermic reaction mixture for use in incoporating alloying element in molten metal comprising iron, an alloying element, silicon and sodium nitrate, the sodium nitrate and the silicon being present in the reaction mixture in proportions by weight equivalent to not more than about 2.42 parts of sodium nitrate to 1.0 part of silicon and in amounts such as to be capable upon ignition of the reaction mixture of generating by reaction sufficient heat to melt the iron and alloying element.

3. An exothermic reaction mixture for use in incorporating an alloying element in molten metal consisting essentially of iron, an alloying element, silicon and sodium nitrate and in which sodium nitrate and silicon are present in proportions by weight equivalent to not more than about 2.5 parts of sodium nitrate to 1.0 part of silicon.

4. An exothermic reaction mixture for use in incorporating chromium in molten metal consisting essentially of iron, chromium, silicon and sodium nitrate and in which sodium nitrate and silicon are present in proportions by weight equivalent to not more than about 2.5 parts of sodium nitrate to 1.0 part of silicon.

5. An exothermic reaction mixture for use in incorporating manganese in molten metal consisting essentially of iron, manganese, silicon and sodium nitrate and in which sodium nitrate and silicon are present in proportions by weight equivalent to not more than about 2.5 parts of sodium nitrate to 1.0 part of silicon.

6. An exothermic reaction mixture for use in incorporating vanadium in molten metal con sisting essentially of iron, vanadium, silicon and sodium nitrate and in which sodium nitrate and silicon are present in proportions by weight equivalent to not more than about 2.5 parts of sodium nitrate to 1.0 part of silicon.

7. An exothermic reaction mixture for use in incorporating chromium in molten metal con sisting essentially of ferrochrome silicon and sodium nitrate and in which sodium nitrate and silicon are present in proportions by weight equiv alent to not more than about 2.5 parts of sodium nitrate to 1.0 part of silicon.

8. An exothermic reaction mixture for use in incorporating manganese in molten metal consisting essentially of ferromanganese silicon and sodium nitrate and in which sodium nitrate and silicon are present in proportions by weight equivalent to not more than about 2.5 parts of sodium nitrate to 1.0 part of silicon.

9. An exothermic reaction mixture for use in incorporating vanadium in molten metal consisting essentially of ferrovanadium silicon and sodium nitrate and in which sodium nitrate and silicon are present in proportions by weight equivalent to not more than about 2.5 parts of sodium nitrate to 1.0 part of silicon.

10. In the production of an exothermic reaction mixture consisting of iron, an alloying elelit .n odium nitrate and ment, silicon and sodium nitrate, the improvement which comprises incorporating in the mixture sodium nitrate and silicon in proportions by weight equivalent to not more than about 2.5 parts of sodium nitrate to 1.0 part of silicon.

11. In the production of an exothermic reaction mixture consisting of iron, an alloying element, silicon and sodium nitrate, the improvement which comprises incorporating in the mixture sodium nitrate and silicon in proportions by weight equivalent to not more than about 2.42 parts of sodium nitrate to 1.0 part of silicon.

12. The method of incorporating an alloying element in molten metal which comprises igniting in contact with the molten metal an exothermic reaction mixture comprising iron, an alloying element, silicon and sodium nitrate, the the silicon being present in the reaction mixture in proportions by weight equivalent to not more than 2.42 parts of sodium nitrate to 1.0 part of silicon.

1 he method of incorporating an alloying element in molten metal which comprises igniting in contact with the molten metal an exothermic reaction mixture consisting of iron, an alloying element, silicon and sodium nitrate, the sodium nitrate and the silicon being present in the reaction mixture in proportions by weight equivalent to not more than 2.5 parts of sodium nitrate to 1.0 part of silicon and in amounts such as to be capable upon ignition of the reaction mixture of generating by reaction suilicient heat to melt the iron and alloying element.

14. The method of incorporating an alloying element in molten metal which comprises igniting in contact with the molten metal an exothermic reaction mixtur consisting of iron, an alloying element, silicon and sodium nitrate, the sodium nitrate and the silicon being present in the reaction mixture in proportions by weight equivalent to not more than 2.42 parts of sodium nitrate to 1.0 part of silicon and in amounts such as to be capable upon ignition of the reaction mixture of generating by reaction sufficient heat to melt the iron and alloying element.

15. The method of incorporating an alloying element in molten metal which comprises igniting in contact with the molten metal an exothermic reaction mixture consisting essentially of iron, an alloying element, silicon and sodium nitrate and in which sodium nitrate and silicon are present in proportions by weight equivalent to not more than about 2.5 parts of sodium nitrate to 1.0 part of silicon.

16. The method of incorporating chromium in molten metal which comprises igniting in contact with the molten metal an exothermic reaction mixture consisting essentially of iron, chromium,

silicon and sodium nitrate and in which sodium nitrate and silicon are present in pro'portions by weight equivalent to not more than about 2.5 parts of sodium nitrate to 1.0 part of silicon.

17. The method of incorporating manganese in molten metal which comprises igniting in contact with the molten metal an exothermic reaction mixture consisting essentially of iron, manganese, silicon and sodium nitrate and in which sodium nitrate and silicon are present in proportions by weight equivalent to not more than about 2.5 parts of sodium nitrate to 1.0 part of silicon.

18. The method of incorporating vanadium in molten metal which comprises igniting in contact with the molten metal an exothermic reaction mixture consisting essentially of iron, vanadium, silicon and sodium nitrate and in which sodium nitrate and silicon are present in propor- I tions by weight equivalent to not more than about 2.5 parts of sodium nitrate to 1.0 part of silicon. 19. The method of incorporating chromium in molten metal which comprises igniting in contact with the molten metal an exothermic reaction mixture consisting essentially of ferrochrome silicon and sodium nitrate and in which sodium nitrate and silicon are present in proportions by weight equivalent to not more than about 2.5 parts of sodium nitrate to 1.0 part of silicon.

20. The method of incorporating manganese in molten metal which comprises igniting in contact with the molten metal an exothermic reaction mixture consisting essentially of ferromanganese silicon and sodium nitrate and silicon are present in proportions by weight equivalent to not more than about 2.5 parts or sodium nitrate to 1.0 part or silicon.

21. The method of incorporating vanadium in molten metal which comprises igniting in contact with the molten metal an exothermic reaction mixture consisting essentially of ferrovanadium silicon and sodium nitrate and in which sodium nitrate and silicon are present in proportions by weight equivalent to not more than about 2.5 parts of sodium nitrate to 1.0 part of silicon.

MARVIN J. UDY.

sodium nitrate and in which 

